Complex systems provides tools with which one can analyse and understand many important problems and processes in social-ecological systems (the coupled systems of humans and nature that comprise our world). Utilising my background in theoretical physics, I have used mathematical methods and concepts including bifurcation analysis, stochastic dynamical systems, generalised modelling, field theory, network theory and slow-fast systems in a broad range of interdisciplinary projects. The fields of application span ecology, sociology, psychology and cell biology, working intensively in collaboration with researchers from those disciplines. At the Stockholm Resilience Centre, I work on a variety of topics involving resilience and sustainability ranging from persistent poverty to climate change to fisheries. I am currently working on the interactions between the Planetary Boundaries and am passionate about advancing resilience theory.